They’ll Take Two in the Bush – Crows and Ravens Show Patience

We live in an “act now!” world that frequently tests us, luring us with temptations and encouraging us to indulge. We may clearly see the importance of living within our budget yet still be dazzled by the shiny appeal of that new sports car; we may strongly believe in the benefits of a healthy diet yet still be weakened with lust for that large slab of double chocolate cake.

Nevertheless, we do sometimes succeed in delaying immediate gratification for the sake of something better in the future, in remembering those clichés about “good things come to those who wait” that our parents and grandparents inflicted on us. Undoubtedly, this is something we’re able to achieve because we’re humans, because we can be goal-directed and can prevail over our impulses, because we are more than unthinking animals who are captives to their immediate needs. Right?

Not so fast.

It is true that many animals seem unable to defer gratification, with prior experiments showing that animals such as rats, pigeons and chickens will rarely choose a delayed food reward over an immediate one, even if the delayed reward is much more attractive and the delay is only a few seconds. (From an evolutionary standpoint, this sort of impatience may make a lot of sense when an animal faces competition and future opportunities for food are unknown. “Life is uncertain, have dessert first!”)

To date, the major exception has appeared to be in primates: chimpanzees, bonobos, rhesus macaques and capuchin monkeys have demonstrated that they can wait for up to five minutes or so if that enables them to obtain a desirable food reward – a level of performance comparable to that of humans. (Interestingly, tests have shown that we humans seem to be much better at deferring money rewards than food rewards. Perhaps this, too, has a basis in natural selection, as food has been obviously always been an imperative, whereas money has existed for only an evolutionary blink of the eye.)

Also, while all of this might lead one to conclude that the ability to delay gratification lies solely within the province of humans and our closest relatives, it now turns out that corvids, the famously smart bird family (see prior AnimalWise posts here and here and here and here) that includes ravens and crows, may be every bit as patient.

As described in a paper published last week in Biology Letters, a team led by Valérie Dufour of the University of Strasbourg recently found that crows (Corvus corone) and ravens (Corvus corax) are able to tolerate delays of over five minutes in order to obtain a better reward, and that they may use the same sort of tactics to distract themselves while they wait as humans do.

In this study, six crows and six ravens were first trained to exchange tokens for food rewards, and then were given a series of “delayed exchange” tests. In each test, a bird would be handed an initial piece of food, which it could either eat immediately or, upon receipt of a signal after a designated waiting period, exchange for a more a desirable reward that it could see throughout the testing period. If the bird ate the initial reward or tried to exchange it too early, the test would end, but if it waited until the proper signal after the waiting period had elapsed – success, a better reward!

The researchers ran the tests with different types of reward (which they labeled as low-, medium- and high-quality) and with varying waiting periods (from 2 to 640 seconds).

Not surprisingly, the birds were generally more willing to exchange for the most highly preferred rewards and, as the following graphic illustrates, had a harder time as the delay period increased (with both crows and ravens maxing out at 320 seconds, or slightly over five minutes):

Interestingly, when the birds had to wait 20 seconds or longer before being able to exchange, they usually placed the “reward in the hand” on the ground and/or cached it in nearby crevices. The researchers believed this to be a distractive strategy, as “[t]hese behaviours probably alleviate the cost of waiting: not having to hold the food distracts the bird’s attention from it.”

As someone who routinely has to put snack food out of reach or even out of sight in order to prevent Homer Simpson-like devouring, this explanation makes a lot of sense to me. (For those of you who would prefer a more uplifting example of a strategy for avoiding temptation, I invite you to think about Ulysses having himself lashed to his ship’s mast so that he can safely listen to the songs of the Sirens.)

In any event, delaying gratification is significant because it involves, on some level, making a judgment about the future and the likelihood of achieving a prospective reward. While it’s not clear whether this entails a full “sense of self,” it is worth (re)noting that corvids are one of the few animals that have demonstrated the ability to recognize themselves in mirrors, a cognitive test that’s often used to measure whether an animal has at least rudimentary self-awareness.

4 Comments

Might the caching behavior be a strategy to get both rewards? Hide the initial, less attractive reward to get it later; meanwhile, wait to collect the better reward. Assuming the researchers removed the cached food or the bird, I wouldn’t expect the strategy to persist, but it would be interesting to try it both ways–with and without later access to the cached food. Either way, the behavior suggests planning ahead.

Good thought! The study itself wasn’t 100% clear on methodology (and I didn’t have access to the supplemental materials that might have provided more detail), but my understanding is that the birds had to give back the initial reward in order to get the more attractive delayed reward.

Also, agreed as to your point regarding planning ahead. One other interesting aspect of the results was that in many of the trials, the birds would make their decision about whether or not to trade “significantly earlier than predicted by chance, i.e. in the first seconds rather than randomly in the course of a trial.” The researchers concluded that this behavior, where the birds would give up early even in trials where the delays were ones they could otherwise have handled, “indicates that they understand something of the duration involved and judge the exchange not worth it.” In other words, they interpreted this as yet another indication of the corvids being able to plan ahead.

Michael

I think this video is not only a great example of delayed gratification (the crow could eat the bread immediately if it wanted) but also an extremely surprising example of tool usage (I just read your article on crows using tools). Not sure where else to post this. This site is really cool though!

That’s awesome! It really does look like the crow is using a small bit of food (bread?) as bait to catch a fish … as you say, delaying gratification and using a tool. I wonder, though, whether it might have been lucky as well as clever. I just found a video on YouTube (below) showing crows dipping bread in water before eating it. Do you think that maybe the fishing crow in your video was doing this (it sort of looks like it’s dipping and eating in the beginning of the footage) and then, after accidentally dropping the food, saw something even better show up? In any event, crows are amazing. Thanks very much for sharing the video!